1. Field of the Invention
The present invention relates to a heat exchanging fin and a method of manufacturing the heat exchanging fin. More precisely, the present invention relates to a heat exchanging fin and a method of manufacutring the heat exchanging fin, in which collars are formed to respectively enclose tube holes, through which heat exchanging tubes will be inserted. Futhermore the collars respectively have flares at their front ends manufactuing the heat exchanging fin.
2. Description of the Related Art
The heat exchanging fin, which is employed in room air conditioners, car air conditioners, etc., includes: a rectangular metallic plate section, which is made of a metal, e.g., aluminum; and a plurality of collared tube holes provided in the metallic plate section with separations and having a prescribed height.
A heat exchanger is assembled by the steps of: piling the heat exchanging fins, in which the collared tube holes are coaxially arranged; inserting heat exchanging tubes, which are made of a metallic material having high heat conductivity, e.g., copper, through the coaxial tube holes; and expanding the heat exchanging tubes, which have been inserted through the tube holes, so as to integrate the heat exchanging tubes with the heat exchanging fins.
The conventional heat exchanging fin is manufactured by the above-mentioned steps by a drawing manner, which is shown in FIGS. 14A-14F, or a drawless manner, which is shown in FIGS. 15A-15D.
In the drawing manner, shown in FIGS. 14A-14F, a shallow projected section 106, which has a columnar shape or a truncated cone shape, is formed in a thin aluminium plate section 100 (see FIG. 14A). The diameter of the shallow projected section 106 is greater than that of the collared tube holes to be formed. The diameter of the shallow projected section 106 is then reduced and the height thereof is gradually increased by drawing the shallow projected section 106 (see FIGS. 14B-14D).
A top face of the projected section 109, which is formed by drawing the shallow projected section 106 until reaching a prescribed height, is opened and burred to make a cylindrical section 104 (see FIG. 14E). Furthermore, a flare 105 is formed by bending a top end of the cylindrical section 104 (see FIG. 14F).
In the drawless manner, shown in FIGS. 15A-15D, a base hole 101, which is enclosed by a projected part 102, is formed by boring and burring the metallic plate section 100 (see FIG. 15A). The diameter of the base hole 101 is then made greater and the projected part 102 is squeezed until a cylindrical section 104 which has a prescribed height is formed (see FIGS. 15B and 15C).
The flare 105 is formed by bending the top end of the cylindrical section 104 (see FIG. 15D).
The heat exchanging fins having collared tube holes, which include the cylindrical sections 104 and the flares 105, are formed by the manner shown in FIGS. 14A-14F or FIGS. 15A-15D. When the heat exchanging fins are piled, the flares 105 of one heat exchanging fin contact a bottom face of the adjacent heat exchanging fin, so that the separation between the heat exchanging fins can be defined.
In the manner shown in FIGS. 14A-14F or FIGS. 15A-15D, the base hole, which is bored in the top face of the projected section 109 or in the metallic plate section 100, is a circular hole. Furthermore, in the manner shown in FIGS. 14A-14F or FIGS. 15A-15D, the width of the flare 105, which is formed to enclose a circular edge of the top end of the cylindrical section 104, is fixed.
Heat exchanging fins of today must be made light in weight. Therefore, the thickness of the metallic plate section 100 must be made thinner.
On the other hand, tough heat exchanging fins are also required. Namely, heat exchanging fins, which are not only thin but also tough, are required. Therefore the metallic plate section 100 must be made of a thin and tough metallic material.
Extensibility of the thin and tough metallic material is less than that of a thick and soft metallic material. Therefore, it is improper for the thin and tough metallic material to be pressed to form heat exchanging fins. When the flare 105 is formed by bending the top end of the cylindrical section 104, the flare 105 is outwardly pulled. When thin and tough material having a small extensibility is used, a crack 106 may be formed in the flare 105 (see FIG. 16) because the end of the flare 105 is extremely extended.